A conduit system may include a set of tubes, pipes, or other conduits for electrical and mechanical wires, connectors, and other components. Conduits may be used to protect electrical or mechanical components in the conduit system. Two rigid conduits can be secured to each other end-to-end using a coupling 1 shown in FIG. 1. One end of the coupling 1 is first inserted into a first conduit 10 having an expanded end portion 12. To secure a second conduit to the coupling 1, the second conduit would be inserted through a nut 3 and a compression ring 5, and into coupling 1. The nut 3 is then screwed onto coupling 1 to compress the compression ring 5 and grip the second conduit. Such an assembly, however, is not watertight. In wet locations where the conduits are exposed to rain, for example, fluids are not restricted from seeping past the coupling and into the conduits. This can damage the components inside the conduits. What is needed is a coupling assembly and method of securing conduits to each other that is convenient to use and that resists rainwater and other liquids.